Layer forming method and apparatus

ABSTRACT

There is provided a method and apparatus for forming a layer, by sequentially repeating a layer deposition cycle to process a substrate disposed in a reaction chamber. The deposition cycle comprising:supplying a first precursor into the reaction chamber for a first pulse period;supplying a second precursor into the reaction chamber for a second pulse period. At least one of the first and second precursors may be supplied into the reaction chamber for a pretreatment period longer than the first or second pulse period before sequentially repeating the deposition cycles.

FIELD

The present disclosure generally relates to a method and an apparatus toform a layer on a substrate. More particularly, the disclosure relatesto sequentially repeating a deposition cycle to form at least a part ofthe layer on the substrate for the manufacturing of a semiconductordevice.

BACKGROUND

A substrate placed in a reaction space may be subjected to alternatingpulses of at least two different precursors suitable for producing adesired thin layer on the substrate. When the substrate is exposed to apulse of the first precursor, a layer of the first precursor or reactionproducts of the first precursor may be formed on the surface of thesubstrate. For example, a silicon halide molecule may chemisorb on asurface site that has a hydroxyl group. The silicon halide may beH₂SiCl₂ which may chemisorb as a H₂SiCl reaction product, with HClreleased as a gaseous byproduct.

The excess of the first precursor may then be removed from the surface,for example by purging the reaction space with an inert gas and/orevacuating the reaction space. Subsequently, the substrate may beexposed to a pulse of a second precursor reactant, which chemicallyreacts with the adsorbed portion of the first precursor reactantmolecules. Fragments of the second precursor reactant will be adsorbedunder some reaction conditions.

For example, when ammonia (NH₃) is used as the second precursor reactantit may leave fragments such as N, NH or NH₂ groups in the layer.Reaction conditions such as temperature and pressure may be chosen toensure that a required layer of the first or second precursor may becreated. In this way the growth of the film proceeds layer by layer.

It has been found that there may be a need to improve the quality of thedeposited layers.

SUMMARY

Accordingly in an embodiment, there is provided a method of forming alayer, comprising:

-   -   providing a substrate in a reaction chamber;    -   sequentially repeating a deposition cycle to deposit at least a        portion of the layer on the substrate disposed in the reaction        chamber, the deposition cycle comprising:    -   supplying a first precursor into the reaction chamber for a        first pulse period;    -   removing a portion of the first precursor from the reaction        chamber;    -   supplying a second precursor into the reaction chamber for a        second pulse period, and    -   removing a portion of the second precursor from the reaction        chamber. At least one of the first and second precursors may be        supplied into the reaction chamber for a pretreatment period        longer than the first or second pulse period before sequentially        repeating the deposition cycles.

At least one of the first and second precursor may react into byproductsin the reaction chamber during the pretreatment period. By supplying atleast one of the first and second precursor in the reaction chamber forthe pretreatment period longer than the first or second cycle period,the byproduct may be more uniformly spread through the reaction chamber.Since byproducts may play an important role in preparing the baresurface for deposition of the first, nucleation layer, the uniformity ofthe nucleation layer may be improved when the byproduct may be betterspread through the reaction chamber during the pretreatment period. Theuniformity of the first, nucleation layer may have a large influence onthe quality of the deposited layer afterwards since subsequent layersmay be more easily deposited on the nucleation layer.

It may be that, during the pretreatment period, the surface may beprepared uniformly for the nucleation layer, but that no actualnucleation layer is deposited. It may also be that, during thepretreatment period, a thin nucleation layer may be deposited.

According to an embodiment there is provided a deposition apparatuscomprising:

-   -   a reaction chamber constructed and arranged to hold at least a        first substrate;    -   a gas distribution and removal system to provide to and remove        from the reaction chamber a first or second precursor; and,    -   a sequence controller operably connected to the gas distribution        and removal system and comprising a memory provided with a        program to execute deposition of a material on the substrate        with the gas distribution and removal system by:    -   sequentially repeating a deposition cycle to deposit at least a        portion of the layer on the substrate disposed in the reaction        chamber, the cycle comprising:        -   supplying a first precursor into the reaction chamber for a            first pulse period;        -   removing a portion of the first precursor from the reaction            chamber;        -   supplying a second precursor into the reaction chamber for a            second pulse period, and        -   removing a portion of the second precursor from the reaction            chamber;    -   wherein the program in the memory is further programmed to        control the gas distribution and removal system to supply at        least one of the first and second precursors into the reaction        chamber for a pretreatment period longer than the first or        second pulse period before sequentially repeating the deposition        cycles.

In some other embodiments, a method for semiconductor processing may beprovided. The method includes depositing a silicon film on a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart illustrating a method of depositing a layeraccording to an embodiment.

DETAILED DESCRIPTION

A silicon nitride (SIN) layer may be used as an insulating film in asemiconductor device. The SiN layer may be deposited in a verticalfurnace apparatus of the batch type by chemical vapor deposition (CVD)on a plurality of semiconductor wafers. During deposition, alternately,a Si source gas and a nitriding gas may be supplied to repeat reactionsto form a layer. For example, dichlorosilane (DCS: SiH₂Cl₂ may be usedas the Si source, and ammonia (NH₃) may be used as the nitriding gas.

The SiN layer may also be deposited by using atomic layer deposition(ALD) techniques. In the case of atomic layer deposition (ALD) thereaction may be chemically self-limiting because the first precursorwill not adsorb or react with the portion of the first precursor thathas already been adsorbed on the substrate surface.

FIG. 1 shows a flowchart illustrating a method of depositing a layer 1according to an embodiment. Such method of forming a layer may be Ntimes sequentially repeating a deposition cycle 3 to process a substratedisposed in a reaction chamber. The cycle may comprise supplying 5 afirst precursor into the reaction chamber for a first pulse period T1and removing 7 a portion of the first precursor from the reactionchamber for a first removal period R1. Further the cycle may comprisesupplying 9 a second precursor into the reaction chamber for a secondpulse period T2 and removing 11 a portion of the second precursor fromthe reaction chamber for a second removal period R2. A portion of thefirst and second precursor may form at least a portion of the layer onthe substrate.

The precursors may be gasses, which may be vaporized liquids, whichreact with each other. The uniformity of the deposited layer on thesubstrate may be very important. For example, the thickness of thedeposited layer over the substrate should be substantially the same overthe surface of the substrate for a good uniformity. Further if multiplesubstrates are processed simultaneously the uniformity of all thedifferent wafers should be the same.

To improve the uniformity at least one of the first and secondprecursors may be supplied into the reaction chamber for a pretreatmentperiod 13 longer than the first or second cycle period beforesequentially repeating the cycles. The first and second precursor mayreact into byproducts in the reaction chamber. By supplying at least oneof the first and second precursor the reaction chamber for thepretreatment period longer than the first or second pulse period ahigher concentration of the byproduct may be generated over a longerperiod. The byproduct may be more uniformly spread through the reactionchamber during the pretreatment period. Since byproducts may play animportant role in preparing the bare surface for deposition of thefirst, nucleation layer, the uniformity of the nucleation layer may beimproved when the byproduct may be better spread through the reactionchamber during the pretreatment period. The uniformity of the firstnucleation layer may have a large influence on the uniformity andtherefore the quality of the deposited layer.

It may be that, during the pretreatment period 13, the surface may beprepared for the nucleation layer and that no actual nucleation layer isdeposited. For example, if only one of the first and second precursor isprovided, the reaction forming the layer may not be initiated. It mayalso be that, during the pretreatment period, a thin nucleation layermay be deposited.

The pretreatment may be beneficial when the reactivity of the baresubstrate is different than the deposited layer. The mix of reactantduring the pretreatment may deposit a nucleation layer or prepare thebase surface for improved deposition. Therefore a delay of thedeposition process on the substrate may be circumvented and theuniformity improved.

The pretreatment period 13 may be between 2 to 1200, preferably 8 to300, more preferably 12 to 100 and most preferably between 15 and 40times longer than the first or second pulse periods. The pretreatmentperiod may be between 1 to 60, preferably 2 to 40, more preferably 5 to20 and most preferably 8 to 15 minutes. The exact time of thepretreatment period may be calibrated by varying the pretreatmentperiods and measuring the uniformity of the deposited layers to selectthe optimal pretreatment period.

Sequentially repeating the deposition cycle takes between 1 to 180,preferably 10 to 140 more preferably 20 to 100 and most preferably 40 to80 minutes. The first and second pulse period 5, 9 may take 1 to 180,preferably 5 to 120, more preferably 8 to 80 and most preferably 10 to50 seconds. The first and second pulse period may be the same or theymay be different. The first pulse period may be longer than the secondpulse period.

The pressure in the reaction chamber is between 0.1 and 1000, preferably1 and 100, and more preferably 6 and 60 Pa during the pretreatmentperiod 13 and/or the deposition period. The temperature may be between300 and 900, preferably 500 and 800, more preferably 600 to 700° C.

The first precursor may comprise a silicon halide. The silicon halidemay comprises fluorine (F), chlorine (Cl), bromine (Br), or iodine (I).At least some of the suitable first precursors may have the followinggeneral formula:H_(2n+2−y)Si_(n)X_(y)

wherein, n=1-10, y=1 or more (and up to 2n+2), and X is F, Cl, I or Brand more preferably n=1-3 and most preferably 1-2. The silicon halidemay be a chlorosilane, dichlorosilane (DCS), trichlorosilane,tetrachlorosilane, iodosilane, diiodosilane, tribromosilane, silicicacid, tetraiodosilane, tetrabromosilane, tetrafluorosilane,chlorotrifluorosilane, dichlorodifluorosilane, or atrichlorofluorosilanedichlorsilane.

The second precursor may comprise a nitriding gas such as for examplehydronitrogens. The hydronitrogens may be ammonia (NH₃) or hydrazine(N₂H₄). The second precursor may be activated by plasma-excitation ornot.

The second precursor may comprises an oxidizing gas such as for exampleoxygen, water or hydrogenperoxide. The terms first or second precursorare not intended to refer to the order in which the precursor aresupplied to the reaction chamber. One could start with the secondprecursor and then continue with the first precursor without adverselyaffecting the deposited layer.

The first precursor may be supplied to the reaction chamber between 1and 20, preferably 1.5 and 4, and more preferably between 2 to 3 timeslonger than the second precursor during the deposition cycle 3. In thisway the stoichiometry of the deposited layer may be varied.

Both the first and second precursor may also be supplied into thereaction chamber simultaneously for the pretreatment period 13 and athin nucleation layer may be deposited. The thin layer may be onemonolayer thick.

It may however also be the case that both the first and second precursormay also be supplied into the reaction chamber simultaneously for thepretreatment period 13 and no thin nucleation layer may be deposited.The later may depend on the length of the pretreatment period and otherprocess parameters.

The first precursor may be removed from the reaction chamber for a firstremoval period R1 and the second precursor may be removed from thereaction chamber for a second removal period R2 during the depositioncycle. The first and/or second removal period may be between 1 to 120,preferably 5 to 60 more preferably 10 to 30 and most preferably 20 to 40seconds. The first and/or second precursor may be removed with a pump. Apurge gas may be provided during removing the first and/or secondprecursor from the reaction chamber.

The amount of the second precursor supplied to the reaction chamber maybe between 1 and 25, preferably between 2 to 15 times more than thefirst precursor supplied to the reaction chamber during sequentiallyrepeating the deposition cycles. In this way the stoichiometry of thedeposited layer may be varied.

The deposition cycles may be repeated between 2 to 100, preferably 10 to60, and more preferably 20 to 50 times. In this way a layer of therequired thickness may be deposited.

The silicon concentration in the deposited layer of SiN may be between 1to 25 or even 33% higher than stoichiometric concentration of silicon inSi₃N₄. Such a layer may have a decreased stress level with respect tostoichiometric Si₃N₄.

The first and second precursor may react with each other to form thelayer on the substrate in an atomic layer deposition (ALD) process. Inthis way the layer may have the benefits from the ALD process. Forexample a lower hydrogen and chloride content may be found in the ALDdeposited layer because there is a bit more time in the ALD process toremove the hydrogen from the layer. Due to less impurities, the qualityof the ALD deposited SiN layer, such as the wet etch rate may be betterat the same temperature. Also the ALD process may create a siliconnitride layer with an improved conformality to prefabricated features onthe substrate. The nucleation of the ALD process may also benefit fromthe continuous supply of at least one of the and second precursors inthe pretreatment period.

A dopant may be provided to alter the properties of the deposited layer.The dopant may comprises carbon, such as for example CH₄, C₂H₂, C₂H₄.The dopant may be oxygen-containing chemical species, for exampleoxidizing species such as oxygen (O₂) and oxygen-containing compounds,including NO, N₂O, NO₂, CO₂, H₂O, and alcohols. In some embodiments, thedopant may be PH₃, AsH₃, and SbH₃.

The layer may be deposited with a deposition apparatus comprising:

-   -   a reaction chamber constructed and arranged to hold at least a        first substrate;    -   a gas distribution and removal system to provide to and remove        from the reaction chamber a first or second precursor; and,    -   a sequence controller operably connected to the gas distribution        and removal system and comprising a memory provided with a        program to execute deposition of a material on the substrate        with the gas distribution and removal system by:    -   sequentially repeating a deposition cycle to deposit at least a        portion of the layer on the substrate disposed in the reaction        chamber, the cycle comprising:        -   supplying a first precursor into the reaction chamber for a            first pulse period;            -   removing a portion of the first precursor from the                reaction chamber;            -   supplying a second precursor into the reaction chamber                for a second pulse period, and            -   removing a portion of the second precursor from the                reaction chamber;    -   wherein the program in the memory is further programmed to        control the gas distribution and removal system to supply at        least one of the first and second precursors into the reaction        chamber for a pretreatment period longer than the first or        second pulse period before sequentially repeating the deposition        cycles.

The method may be performed in a vertical furnace. For example, thedeposition processes may be performed in an A412™ vertical furnaceavailable from ASM International N.V. of Almere, the Netherlands. Thefurnace has a process chamber that can accommodate a load of 100 to 200semiconductor substrates, or wafers, having a diameter of 300 mm, withthe substrates held in a wafer boat. The program may be programmed viathe user interface of the vertical furnace to supply at least one of thefirst and second precursors into the reaction chamber for a pretreatmentperiod longer than the first or second cycle period before sequentiallyrepeating the ALD cycles.

An example of a process for the deposition of the silicon nitride mayhave the following conditions as depicted in table 1:

TABLE 1 According Process name Reference to embodiment Pre-treatment NoDCS/NH3 Pretreatment period (s) 600 Pressure (Pa) 26 NH3 flow (sccm) 300DCS flow (sccm) 60 N2 flow (sccm) 30 Pulse DCS First pulse time (s) 4040 Pressure (Pa) 13 13 DCS flow (sccm) 200 200 N2 flow (sccm) 30 30Pulse NH3 Second pulse time (s) 15 15 Pressure (Pa) 13 13 NH3 flow(sccm) 250 250 N2 flow (sccm) 30 30 Purge pulse Pressure (Pa) 26 26 N2flow (sccm) 1000 1000 Temperature ° C. 650 650 uniformity of thethickness over the substrate 2 0.4 for the worst substrate (Å).uniformity of the thickness over the substrate 0.4 0.4 for the bestsubstrate (Å).

It will be appreciated by those skilled in the art that variousomissions, additions and modifications can be made to the processes andstructures described above without departing from the scope of theinvention. It is contemplated that various combinations orsub-combinations of the specific features and aspects of the embodimentsmay be made and still fall within the scope of the description. Variousfeatures and aspects of the disclosed embodiments can be combined with,or substituted for, one another in order. All such modifications andchanges are intended to fall within the scope of the invention, asdefined by the appended claims.

What is claimed is:
 1. A method of forming a layer comprising siliconnitride, comprising: providing a substrate in a reaction chamber;performing a pretreatment step for a pretreatment period; after thepretreatment step, sequentially repeating a deposition cycle to depositat least a portion of the layer on the substrate disposed in thereaction chamber, the deposition cycle comprising: supplying a firstprecursor into the reaction chamber for a first pulse period; removing aportion of the first precursor from the reaction chamber; supplying asecond precursor into the reaction chamber for a second pulse period;and removing a portion of the second precursor from the reactionchamber; wherein the first precursor comprises a silicon halide; whereinthe second precursor comprises a nitriding gas; wherein the siliconhalide is supplied into the reaction chamber for the pretreatment periodsuch that the silicon halide is supplied to the reaction chamber duringboth the pretreatment step and the deposition cycle, the pretreatmentperiod being longer than the first or second pulse period; wherein thefirst precursor is supplied to the reaction chamber between 1.5 and 4times longer than the second precursor during sequentially repeating adeposition cycle, and wherein the amount of the second precursorsupplied to the reaction chamber is between 2 and 15 times more than thefirst precursor supplied to the reaction chamber during sequentiallyrepeating a deposition cycle; and wherein both the first precursor andthe second precursor are supplied into the reaction chambersimultaneously during the pretreatment period to deposit a nucleationlayer.
 2. The method according to claim 1, wherein the pretreatmentperiod is between 2 to 1200 times longer than the first or second pulseperiod.
 3. The method according to claim 1, wherein the pretreatmentperiod is between 1 to 60 minutes.
 4. The method according to claim 1,wherein sequentially repeating the deposition cycle takes between 1 to180 minutes.
 5. The method according to claim 1, wherein the first pulseperiod is between 1 to 180 seconds.
 6. The method according to claim 1,wherein the second pulse period is between 1 to 180 seconds.
 7. Themethod according to claim 1, wherein the pressure in the reactionchamber during the pretreatment step is higher than the pressure in thereaction chamber during the deposition cycle.
 8. The method according toclaim 1, wherein the pressure in the reaction chamber during thepretreatment step is at least twice the pressure in the reaction chamberduring the deposition cycle.
 9. The method according to claim 1, whereinthe first precursor is selected from the group consisting ofchlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane,iodosilane, diiodosilane, tribromosilane, silicic acid, tetraiodosilane,tetrabromosilane, tetrafluorosilane, chlorotrifluorosilane,dichlorodifluorosilane, and trichlorofluorosilanedichlorsilane.
 10. Themethod according to claim 1, wherein the second precursor compriseshydrazine (N₂H₄).
 11. The method according to claim 1, wherein the firstor second precursor is not activated by a plasma.
 12. The methodaccording to claim 1, wherein the first precursor comprises at least oneof fluorine, chlorine, bromine, or iodine.
 13. The method according toclaim 1, wherein the nucleation layer is one monolayer thick.
 14. Themethod according to claim 1, wherein the first precursor is supplied tothe reaction chamber between 2 and 3 times longer than the secondprecursor during sequentially repeating a deposition cycle.
 15. Themethod according to claim 1, wherein the deposition cycles are repeatedbetween 2 to 100 times.
 16. The method according to claim 1, wherein thelayer comprises silicon nitride and the silicon concentration in thedeposited layer is between 1 to 33% higher than stoichiometricconcentration of silicon in Si₃N₄—.
 17. The method according to claim 1,wherein the method comprises providing a dopant selected from the groupconsisting of AsH₃ and SbH₃—.
 18. The method according to claim 1,wherein the method is used in a vertical furnace.